Centrifugal discharger mechanism



P 1967 w. GRIESELHUBER 3,339,733

CENTRIFUGAL DISCHARGER MECHANISM Filed March 29, 1965 4 Sheets-Sheet 1 INVENTOR. WH. LIAM GRIESEL HUBER E' li]. ,BY

ATTORNEY p 5, 1967 w, GRIESELHUBER 3,333,733

GBNTRIFUGAL DISCHARGER MECHANISM Filed March 29, 1965 4 Sheets-Sheet 2 INVENTOR. WILLIAM GRIESELHUBER ATTORNEY p 5, 1967 w. GRIESELHUBER 3,339,733

CENTRIFUGAL DISCHARGER MECHANISM Filed March 29, 1965 4 Sheets-Sheet 3 I NVEN TOR.

WILLIAM GRIESELHUBER ATTORNEY United States Patent 3,339,733 CENTRIFUGAL DISCHARGER MECHANISM William Grieselhuber, Hamilton, Ohio, assignor to The Western States Machine Company, Hamilton, Ohio, a corporation of Utah Filed Mar. 29, 1965, Ser. No. 443,386 19 Claims. (Cl. 210-91) This invention relates to a power-operated discharger mechanism for heavy centrifugal machines of the type used for separating liquids from solids in large scale industrial processes.

Power-operated discharger mechanisms have been provided for heavy centrifugal machines, for example, as disclosed in US. Patent No. 2,708,035, issued May 10, 1955, ot Joseph Hertrich. Centrifugal discharger mechanisms of the type disclosed in the foregoing patent include a housing mounted on the curb top of the centrifugal machine for horizontal swinging movement, a vertical discharger shaft carried by the housing in non-rotatable but axially slidable relation thereto and being offset with respect to the axis of the swinging movement of the housing, a discharger shoe secured to the lower end of the shaft and held by the latter within the centrifugal basket, a first fluid-pressure operated means carried by the housing for swinging it in opposition to a spring exerted force so as to move the shoe from an inner rest position outwardly into solids on the basket side wall, and a second fluidpressure operated means carried by the housing for moving the shaft and shoe downwardly after the shoe has been moved outwardly to the basket side wall, thereby to discharge solids from the basket, and, upon inactivation of the first fluid-pressure operated means, to move the shaft and shoe upwardly and thereby cooperate with the spring in returning the shoe to its rest position. The known power-operated centrifugal discharger mechanism further has a fixed member or bracket extending into the basket and definding a horizontal ledge directed toward the discharger shaft and onto which the base of the shoe is displaced by the final inward swinging of the housing so that the ledge prevents the shoe from falling into the basket in the event of a failure in the fluid pressure by which the discharger is operated.

Since the discharger shaft of the above described mechanism swings or moves along an arcuate path during displacement of the shoe outwardly to, and inwardly away from the basket side wall, such discharger mechanism is only suited for use with a centrifugal machine having a centrally open curb top, or at least an opening in the curb top of relatively large extent to permit the necessary swinging movement of the shaft with 'the pivoted discharger housing. The provision of a relatively large opening-in the curb top to accommodate the swinging movements of the discharger shaft does not pose a problem when the space within the curb is to be open to the atinosphere, for example, as in centrifugal machines used for the refining or drying of sugar or dextrose. However, when the space within the curb is to be under pressure or is to contain a toxic or corrosive atmosphere, as in numerous chemical processes, difliculties are experienced in achieving an adequate seal at the opening in the curb top through which the swingable discharger shaft extends. I Accordingly, it is an object of this invention to provide a power-operated discharger mechanism for use in connection with heavy centrifugal machines which are to have the space within the curb sealed from the external atmosphere so as to be capable of being pressurized or of containing a corrosive or toxic atmosphere.

'According to an important feature of this invention, the discharger shoe disposed Within the basket is secured to the lower end of a vertical cylindrical ram which extends th-rough a relatively small opening in the curb top and is mounted both for axial movement to effect the downward and upward displacements of the shoe and for turning about the longitudinal axisof the ram to effect the outward displacement of the shoe to the basket side wall and the inward return tof the shoe to its rest position. Since the necessary movements of the shoe during the discharging cycle are achieved merely by axial displacements of the ram and turning of the latter about its own axis, the escape of fluid under pressure through the curb top opening from the space within the curb is prevented simply by an annular seal slidably embracing the ram at the curb top. Such seal is further preferably arranged to present minimal areas or surfaces for contact by the atmosphere within the curb, thereby to make. economically practical the use of materials in the seal which are resistant to attack by corrosive gases or liquids.

According to another feature of this invention, a latch is provided to normally engage the ram and prevent movement of the shoe from its rest position, and the latch is releasable by fluid under pressure from the same control means which supplied fluid under pressure to operate the actuating means by which the ram is turned and axially displaced to effect the discharging movements of the shoe. Thus, in the event that there is a failure in the pressure of the fluid for elfecting the necessary controlled movements of the discharger shoe, the latch remains engaged for securely holding the shoe in its rest position.

The above, and other objects, features and advantages of the invention, and the several new combinations and constructions which it provides will be apparent from the following detailed description and the accompanying drawings illustrating a preferred embodiment thereof. In the drawings:

FIG. 1 is a side elevational view of a discharger mechanism embodying this invention in assembled relation to a centrifugal basket and curb of which only fragments are shown;

FIG. 2 is a top plan View of the same discharger mechanism;

FIG. 3 is a vertical sectional view taken along the line 3-3 on FIG. 2, but on an enlarged scale;

FIG. 4 is an enlarged horizontal sectional view taken along the line 44 on FIG. 1;

FIG. 5 is a detail sectional view taken along the line 55 on FIG. 1;

FIG. 6 is an enlarged detail sectional view taken along the line 66 on FIG. 2; and

FIG. 7 is a schematic view of the control systems of the discharger mechanism.

The drawings show certain conventional elements of a heavy centrifugal machine of the type for which the illustrated embodiment of this invention is adapted. These conventional elements include a centrifugal basket 1 having a perforated side wall 2 and a cap 3 and being supported by a vertical shaft or spindle (not shown) which is suspended in gyratory manner and rotatably driven by a motor or prime mover (not shown). The entire basket 1 is surrounded by a stationary curb 4 which collects the liquid expelled from the basket and has a curb top 5 providing support for the discharger mechanism 10 embodying this invention.

The discharger mechanism 10 has a shoe 11 mounted within the basket 1, as hereinafter described in detail, for vertical movement, so that its tip or working end 12 can traverse the axial length of the basket between cap 3 and the bottom of the basket, and for horizontal movement so that tip 12 can move generally radially in and out relative to basket side wall 2. It will be noted from FIG. 2 that the discharger shoe 11 extends in such a direction that it will be effective to dig out solids in the '3 basket when the basket is rotated in the direction of the arrow and the shoe is moved outwardly to the basket side wall.

The shoe 11 is secured, at its heel 13, to the lower end of a cylindrical, vertical ram 14 which extends from within the housing through a circular opening 15 in curb top (FIGS. 1 and 3) with relatively small radial clearance therebetween. As shown on FIGS. 3 and S, the secure attachment of shoe 11 to ram 14 may be achieved by providing a cap or end piece 16 at the lower end of the ram with a diametrically extending projection 17 on its lower surface which engages in a diametrically recessed groove in shoe heel 13. The attachment of shoe 11 to ram 14 is completed by screws 19 extending upwardly through. the bottom of heel 13 and tightened into tapped holes formed in bottom cap 16 at the opposite sides of projection 17.

As shown on FIG. 3, ram 147may be formed of an elongated tubular body 20 of suflicient strength to resist the forces imposed thereon during operation of the discharger mechanism and being enveloped, along substantially its entire length, by a thin-wall protective sleeve 21 of corrosion resistant metal. The lower end of protective sleeve 21 is welded, as at 22, to the cap 16 for holding the latter in assembled relationship to the lower end of tubular body 20, and the upper end edge of protective sleeve 21 is welded to tubular body 20 adjacent the upper end of the latter, as at 23.

The ram 14 is mounted for turning about its longitudinal axis and for axial movement through curb top opening 15 by means of a support assembly 24. Assembly 24 includes a base 25 which is secured by bolts 26 on curb top 5 with a gasket 27 therebetween (FIG. 3), and which extends around curb top opening 15. Extending upwardly from base 25, and integral therewith, is a hollow, generally cylindricalhousing 28 (FIGS. 1, 2 and 3) having its lower portion formed with diametrically opposed cutouts 29. The housing 28 defines an upwardly stepped cylindrical cavity 30 (FIG. 3) and has an inwardly directed annular flange 31 forming a ledge at the bottom of cavity 30 immediately above the diametrically opposed cutouts or openings 29. An annular bearing. member 32 is pressed in the lower portion of cavity 30. Support assembly 24 further includes a vertical support cylinder 33 fitting turnably within bearing member 32. A ring 34 (FIGS. 1, 3 and 4) is suitably secured on the lower end portion of support cylinder 33 so as to be positioned within cavity 30 immediately above bearing member 32. Cylinder 33 is held in assembled relation to housing 28 by means of a retaining sleeve 35 which extends around cylinder 33 above ring 34 and has an outwardly directed lower flange 36 seating on top of housing 28 and secured to the latter by means of bolts 37.

An assembly of split bearing 38 is arranged within the lower end portion of support cylinder 33 encompassed by housing 28 and sleeve 35, and provides bearing support for ram 14 while permitting axial and turning movements of the latter. A lubrication fitting 39 is provided in sleeve 35 for supplying lubricant to bearing assembly 38. The upper end of bearing assembly 38 seats against an internal radial shoulder 40 in support cylinder 33, and a retaining ring 41 is engageable with the lower end of the bearing assembly and secured by screws 42 to the underside of flange 31. Shims 43 are interposed between retaining ring 41 and flange 31 to permit adjustment of the axial compacting of bearing assembly 38 for removing play from the bearing-support for ram 14. It will be seen that, in thus removing the play in the bearing support for the ram, access to screws 42 and shims 43 with the necessary tools may be had through cutouts 29 at opposite sides of housing 28.

Ram 14 is held against turning relative to support cylinder 33 by means of guide lugs 44 which are welded or otherwise secured at diametrically opposed locations on the upper end portion of tubular body 20 and which extend slidably in diametrically opposed, axial slots 45 formed along substantially the entire length of support cylinder 33 projecting above sleeve 35. Ram 14 and support cylinder 33 are axially dimensioned so that the extent of the axial movement of guide lugs 44 along slots 45 will be sufficient to permit displacement of shoe 11 from its uppermost position (FIGS. 2 and 3) just below cap 3 of basket 1 to its lowermost position immediately above the bottom of the basket.

A head 46 is secured by screws 47 to a flange 48 welded on the upper end of support cylinder 33, and a selected number of shims 49 are interposed between head 46 and flange 48 for permitting adjustment of the extreme positions of the shoe, as hereinafter described in detail.

The axial movements of ram 14 relative to support cylinder 33 are effected by a fluid-pressure operated actuating means 50 (FIG. 3) substantially contained within ram 14. The actuating means 50 includes a cylinder 51 extending axially within tubular body 20 and being closed at its upper and lower ends by cylinder heads 52 and 53, respectively, which are suitably secured, as by lock rings 54, to cylinder 51. A hollow rod 55 extends downwardly within the ram from a flange 56 secured by screws 57 to lower cylinder head 53, and the lower end of rod 55 bears against cap 16 thereby to limit downward displacement of cylinder 51 within ram 14. A retaining ring 58 has external threads engaging internal threads formed in the upper end portion of tubular body 20 so that retaining ring 58 can be screwed downwardly into tubular body 20 to engage the upper cylinder head 52 and thereby hold cylinder 51 against displacement relative to ram 14.

The fluid-pressure operated actuating means 50 further includes a piston 59 located within cylinder 51 and supported by a hollow piston rod 60 which extends upwardly from the piston through suitable seals 61 in upper cylinder head 52. The upper end portion of piston rod 60 projecting from ram 14 extends through a central bore in head 46 and is fixedly secured to the latter, as by a nut 62. Extending axially within hollow piston rod 60, and spaced radially therefrom, is a tube 63. The lower end of tube 63 fits into a plug 64 within the lower end of rod 60, while the upper end of tube 63 is received in a nipple or hose fitting 65 screwed intov the upper end of rod 60. The tube 63 defines an inner passage 66 extending from nipple or fitting 65 and opening through a central aperture 67 at the bottom of piston 59 into the space 51A within cylinder 51 between piston 59 and lower cylinder head 53. The radial clearance between hollow piston rod 60 and tube 63 defines an annular passage 68 which is blocked at its lower and upper ends by plug 64 and fitting 65. A radial bore extending through the wall of piston rod 60 immediately above piston 59 establishes communication between annular passage 68 and the space. 51B within cylinder 51 between the upper cylinder head 52 .and piston 59. The end portion of piston rod 60 extending through head 46 is formed with a radial bore 70 registering with .an annular groove 71 formed in head 46, and the latter further has a passage 72 extending from groove 71 to a tapped socket 73 serving as a hose fitting or nipple. Thus, fluid under pressure supplied to the nipple or hose fitting 73 is conducted through annular passage 68 to the space 51B within cylinder 51 above piston 59 and, by reason of the fact that piston 59 is held against axial displacement by the attachment of 51 below piston 59, thereby to act downwardly against the lower cylinder head 53. The limits of the upward and downward displacements of ram 14 and shoe 11 are determined by the engagement of the lower and upper cylinder heads 53 and 52, respectively, with fixed piston 59. Since piston 59 is in fixed relation to the head 46 of support cylinder 33, it will be apparent that the addition or removal of shims 49 between head 46 and flange 48 of cylinder 33 is effective to adjust the vertical position of the fixed piston relative to curb top 5, and hence is effective to adjust the uppermost and lowermost positions of shoe 11 relative to basket 1.

Turning of ram 14 about its longitudinal axis so as to swing shoe 11 in the direction for moving its working tip 12 outwardly to basket side wall 2 is effected by a second fluid-pressure operated actuating means 74 (FIGS. 1 and 2). The actuating means 74 includes a cylinder 75 having an ear 76 extending from one end and being pivotally mounted on a pin 77 carried by a post 78 projecting upwardly from base 25. A piston 79 is slidable within cylinder 75 and has a piston rod 80 extending therefrom axially out of the cylinder. A clevis 81 is secured on the outer end of piston rod 80 and is pivotally connected by a pin 82 to an ear 83 (FIGS. 1 and 4) formed on an arm 84 which extends radially outward from ring 34 through a slot 85 of suitable angular extent formed in housing 28. The end portion of cylinder 75 adjacent the ear 76 has a nipple or hose fitting 86 (FIG. 2) through which fluid under pressure can be admitted to the space 87 in cylinder 75 to effect movement of piston 79 toward the right, as viewed on FIG. 1, that is, in the direction for extending piston rod 80. The extension of piston rod 80 causes angular displacement of arm 84 and support cylinder 33, and hence also of ram 14, in the counter-clockwise direction, as viewed on FIG. 2, for moving the working tip 12 of shoe 11 outwardly from the illustrated rest position to basket side wall 2.

In order to effect inward return movement of the shoe to its rest position, helical tension springs 88 are arranged above and below cylinder 75 and connected, at their oppostie ends, to the pivot pin 82 extending above and below clevis 81, and to an anchor pin 89 projecting upwardly from post 78. It will be apparent that spring 88 yieldably urge support cylinder 33 and ram 14 to turn in the clockwise direction, as viewed on FIG. 2, thereby to normally hold shoe 11 at its rest position radially inward from basket side wall 2, and that the pressure of the fluid admitted to space 87 in cylinder 75 for moving shoe 11 outwardly to the basket side wall is sufiicient to exert a force on piston 79 capable of overcoming the yieldable force of spring 88.

Since movements of shoe 11 outwardly to, and inwardly away from basket side wall 2 and axially along the basket are all accomplished merely by turning of ram 14 about its longitudinal axis and by axial displacement of the ram, the curb top opening 15 can be circular and only slightly larger than the outer cross-sectional area of ram 14. This facilitates the attainment of an effective seal around the ram for preventing the escape through the opening in holder 90 of either pressure or a corrosive atmosphere from the space within curb 4. As shown particularly on FIG. 3, the seal around ram 14 may include an annular holder 90 secured, as by welding, in base 25, and depending through curb top opening 15. Holder 90 has an inturned annular lip or ledge 91 extending close to the outer surface of ram 14 and supporting a series of sealing rings 92 which slidably embrace ram 14. A retaining ring 93 is screwed downwardly into holder 90 above sealing rings 92 to axially compact the latter against ledge 91 and thereby press the sealing rings radially inward into sealing contact with ram 14. By reason of the minimal surface areas of holder 90 and sealing rings 92 exposed to the atmosphere within curb 4, such elements of the seal can be economically formed of materials which are resistant to corrosive atmospheres. For example, holder 90 may be formed of a highly corrosion-resistant nickel-base alloy, such as that available commercially from Haynes Stellite Company under the trade name Hastelloy C, and which contains 0.15% (maximum) carbon, 13 to 16% chromium, 15 to 19% molybdenum, 3.5 to 5.5% tungsten, 4 to 7% iron, and the balance nickel. A preferred material for the sealing rings 92 is the polytetrafluoroethylene available commercially under the trade name Teflon from E. I. du Pont de Nemours and Company.

Referring now to FIG. 7, it will be seen that the supplying of fluid under pressure to spaces 51A and 51B in cylinder 51, and hence the vertical movements of ram 14, are controlled by a four-way distributing valve 94 which may be mounted on base 25 of the support assembly. The four-way valve 94 includes an elongated valve housing 95 in which a valve spool 96 is axially movable. The spool 96 is urged axially in one direction, that is, toward the left as viewed on FIG. 7, by a spring 97 acting against one end of the spool, and the opposite end of the spool is received in a pilot chamber 98 so that, when fluid under pressure is admitted to pilot chamber 98, valve spool 96 is displaced axially against the force of spring 97 to the position shown on FIG. 7.

Valve housing 95 is provided intermediate its ends with an inlet 99 for fluid under pressure, for example, compressed air, which is supplied thereto by way of a conduit 100 from a compressed air supply header or manifold 101. The hose fittings 65 and 73 on the head 46 of support cylinder 33 are connected by hoses 102 and 103 with ports 104 and 105 provided in valve housing 95. The valve housing further has exhaust ports or vents opening to the atmosphere through restrictors 106 and 106A. Valve spool 96 is provided with spaced apart lands 107 which are arranged so that, when valve spool 96 is in the illustrated position, compressed air entering at inlet 99 is passed through .port 105 to hose 103 and fitting 73, thereby to enter space 51B of cylinder 51 for holding ram 14 in its raised position, while port 104 of valve 94 communicates with the atmosphere through restrictor 106 for venting space 51A through fitting 65 and hose 102. On the other hand, when pilot chamber 98 is vented to the atmosphere, as hereinafter described in detail, so that spring 97 shifts valve 96 toward the left, as viewed on FIG. 7, lands 107 of the valve spool establish communication between compressed air inlet 99 and port 104, and between port 105 and the atmosphere through restrictor 106A, thereby to supply compressed air through hose 102 and fitting 65 to the space 51A of cylinder 51 while the space 51B is vented to the atmosphere so as to effect downward movement of ram 14.

The alternate supplying of compressed air to pilot chamber 98 or the venting of the pilot chamber is achieved by a sequence air valve 108 which, as shown on FIGS. 1 and 2, is supported by a bracket 109 secured on base 25. The valve 108 has an actuating arm 110 urged to a normal position by a spring 111 (FIG. 2) and being connected to a plunger 112 which is slidable in a bearing 113 mounted on bracket 109. As shown, bracket 109 is located on base 25 so that plunger 112 is in the path of movement of the head of a stop screw 114 adjustably carried by arm 84. Thus, upon turning of support cylinder 33 and ram 14 in the direction for moving shoe 11 outwardly to hasket sidewall 2, the head of stop screw 114 comes into engagement with, and acts against plunger 112 to move the latter in opposition to the spring 111 and thereby trip the actuating lever 110 of air sequence valve 108.

As shown on FIG. 7, air sequence valve 108 receives compressed air from conduit 100 through a branch conduit 115 and is, in turn, connected with pilot chamber 98 of valve 94 through a hose or conduit 116. Sequence valve 108 is of a conventional type operative to supply compressed by displacement of plunger 112, then valve 108' chamber 98 so long as its actuating lever 110 is urged to its normal position shown on FIG. 2 by means of spring 111. However, when actuating lever 110 is tripped or depressed by displacement of plunger 112, then valve 108' interrupts the communication between conduits 115 and 116, and establishes communication between conduit 116 and a vent or discharge port which opens to the atmosphere through a restrictor or leak control valve 117.

' The operation of the actuating means 74 is under the control of a valve 118 actuated by a solenoid 119 and connected between compressed air supply header or manifold 101 and a conduit 120 extending to the hose fitting 86 opening into space 87 of cylinder 75. Valve 118 has a discharge port 121 through which space 87 of cylinder 75 is vented to the atmosphere when solenoid 119 is deenergized, and compressed air is supplied through valve 118 and conduit 120 from header 101 to space 87 when solenoid 119 is energized.

In order to control the speed of movement of shoe 11 outwardly tov basket side wall 2 when compressed air is supplied to space 87 of cylinder 75, as described above, the space 122 within cylinder 75 at the side of piston 79 opposed to space 87 is connected through a conduit 123 having a metering orifice or restriction 124 therein with an oil reservoir 125. As shown on FIGS. 1 and 2, oil reservoir 125 may be mounted on base 25 alongside cylinder 75 and may also provide the support for valve 94 on the base. When compressed air is admitted to the space 87 to displace piston 79 and thereby cause horizontal movement of shoe 11 outwardly toward the basket side wall, the speed of such movement is limited by the rate at which oil can be expelled from cylinder space 122 through metering orifice or restriction 124 to oil reservoir 125.

It will be apparent that so long as stop screw 114 carried by arm 84 is spaced from actuating plunger 112 of air sequence valve 108, and compressed air is available from header 101, valve 94 will cause the supplying of compressed air to space 51B of cylinder 51 and the venting of space 51A, whereby ram 14 will be held in its uppermost position. Further, so long as solenoid 119 is deenergized, valve 118 causes venting of space 87 in cylinder 75, so that springs 88 cause turning of ram 14 in the direction moving shoe 11 inwardly away from the basket side wall to the limit of such movement defined by the engagement of arm 84 with the related end of slot 85 in housing 28. When the ram is thus at its uppermost position and turned, in the clockwise direction, as viewed on FIG. 2, to the limit determined by engagement of arm 84 with an end of slot 85, shoe 11 is in its rest or idle position where it cannot interfere, or come into engagement with solids within basket 1 during the high speed rotation of the basket for separating liquids from the solids. However, a failure of the pressure of air supplied through header 101 or a break or leak in any of the conduits 100, 103, 115 and 116, or the connections thereof, would result in a decrease in the pressure applied in space 51B of cylinder 51, and permit the ram 14 and shoe 11 to drop into the basket from the safe rest or idle position of the shoe, thereby creating a hazardous condition in the event that the drop in air pressure in space 51B occurred during'the high speed rotation of the basket.

In order to prevent dropping of shoe 11 from its rest position except when an adequate pressure of air is available from header 101 and a discharge cycle'is initiated, as hereinafter described in detail, the discharger mechanism 10. embodying this invention further includes a latch assembly 126 having a housing 127 suitably secured on support cylinder 33 adjacent the upper end of the latter (FIGS. 1 and 6). As shown particularly on FIG. 6, housing 127 slidably supports a latch bolt 128 which is.

adapted to project radially inward through the wall of support cylinder 33 for engagement in a keeper recess 129 formed in ram 14 adjacent the upper end of the latter. So long as latch bolt 128 is engaged in keeper recess 129, shoe 11.is positively prevented from falling from its rest position. Housing 127 includes a hollow cylindrical outer portion 130 in which an enlarged, piston-like portion 131 of latch bolt 128 is slidable. A helical compression spring 8 132 is interposed between housing portion and piston 131 to continuously urge latch bolt 128 radially inward, that is, to its engaged position in keeper recess 129. A rod 133 extends axially outward from latch bolt 128 and is suitably secured, at its outer end, to a flat-sided member 134 which is movable between guides 135 on housing portion 130 to prevent turning of latch bolt 128 within housing 127. The cylindrical housing portion 130 has an inlet 136 for fluid under pressure opening in front of piston 131. Thus, when fluid under pressure, for example,

compressed air, is supplied to inlet 136, the compressed air acts within housing portion 130 against piston 131 in the direction opposed to the force of spring 132 and moves latch bolt 128 radially outward for disengaging the latch bolt from keeper recess 129 and thereby freeing ram 14 for downward movement.

As shown particularly on FIG. 7, a branch conduit 137 extends from the conduit 120, between solenoid controlled valve 118 and cylinder 75, to inlet 136 of latch.

assembly 126 for supplying compressed air to the latter, and thereby releasing or disengaging the latch bolt only when solenoid 119 is energized to initiate a discharge cycle and when adequate air pressure is available from header 101 for overcoming the force of spring 132.

FIG. 7 further illustrates suitable electric circuits for initiating and controlling the discharge cycle of discharger mechanism 10. As shown, such electrical circuits have, as the major components thereof, a relay 138 for controlling the energization of solenoid 119 from the usual power supply lines L and L a time-delay relay 139 for effecting deenergization of relay 138, a down" limit switch 140 for energizing time delay relay 139, and an up limit switch 141 and in limit switch 142 which cooperate to cause operation of a signal, for example, a lamp 143, which serves to indicate when shoe 11 is in its rest or idle position.

As shown particularly on FIGS. 1 and 3, down limit switch 140 and up limit switch 141 are mounted at vertically spaced apart locations on an upstanding support 144 which is secured to housing 28, as by screws 145 (FIG. 3) and which extends alongside support cylinder 33. Limit switches 140 and 141 have actuating members 146 and 147, respectively, disposed at the inside of memher 144 and being interposed in the path of movement of an arcuate abutment 148 which is welded to the outer end of one of the guide lugs 44 so that abutment 148 moves vertically with ram 14. Switches 140 and 141 each have normally open contacts which are closed when the respective actuating member 146 or 147 is engaged and rocked by abutment 148. Switch 141 is vertically located on member 144 so that its actuating member 147 is rocked by abutment 148 to close the contacts of switch 141 only when ram 14 is in its uppermost position. On the other hand, switch 140 is vertically located so that its actuating member 146 is rocked byabutment 148, thereby to close the contacts of switch 140, only when ram 14 reaches its lowermost position, at which time shoe 11 is immediately above the bottom of basket 1.

As shown on FIGS. 1 and 2, in limit switch 142 is mounted on base 25 so that its actuating member 149 is engaged and rocked by arm 84, thereby to close the normally open contacts of switch 142, when ram 14 is turned about its longitudinal axis to space shoe 11 inwardly from basket side wall 2. Thus, the contacts of switches 141 and 142 are simultaneously closed only when ram 14 is in its uppermost position and shoe 11 is swung inwardly away from the basket side wall, that is, disposed in its rest position. As shown on FIG. 7, the circuit for energizing signal 143 from power supply lines L and 1. has switches 141 and 142 interposed in series therein. Thus, signal 143 is energized only when the contacts of switches 141 and 142 are simultaneously closed to indicate the presence of shoe 11 in its rest position.

Relay 138 has normally open contacts a and b which are closed upon energization of the coil c of the relay. The contacts a of relay 138 are interposed in the energizing circuit 150 for solenoid 119 so that the latter is energized only when coil of relay 138 is energized. The energization of coil c of relay 138 is initiated to start a discharge cycle through a circuit 151 having a normally open, manually actuable push-button switch 152 interposed therein. A hold circuit 152 for the coil c of relay 138 has the normally open hold-contacts b of relay 138 and the normally closed contacts a of time delay relay 139 connected therein in series. Thus, after manual operation of push-button switch 152 for initiating energization of the coil of relay 138, the latter remains energized through its hold contacts b until such time as the contacts a of time delay relay 139 are opened. The energizing circuit 153 for the coil c of time delay relay 139 has the normally open contacts of down limit switch 140 connected in series therein so that time delay relay 139 is energized to effect the delayed opening of its contacts a only when shoe 11 reaches the bottom of basket 1 and abutment 148 rocks actuating member 146 of switch 140 for closing the contacts of the latter.

A complete sequence of automatic operation of discharger mechanism will now be described:

During the operation of the centrifugal machine for separating liquids from solids, the several components of the control system are in the positions illustrated on FIG. 7. More specifically, solenoid 119 of valve 118 is deenergized so that valve 118 vents space 87 of cylinder 75 to permit springs 88 to swing ram 14 in the direction moving shoe 11 inwardly away from the basket side wall to a position where arm 84 actuates in limit switch 142. At the same time, air sequence valve 108 is positioned to supply compressed air to pilot chamber 98 of valve 94 so that the latter supplied compressed air to space 51B of cylinder 50 and vents space 51A, thereby causing ram 14 to move upwardly and similarly raising shoe 11 to the position where abutment 148 actuates up limit switch 141. The simultaneous actuation of switches 141 and 142, as described above, causes energization of signal.

143 indicating that shoe 11 is in its safe rest position.

In order to initiate a discharge cycle, push-button switch 152 is manually actuated to energize coil 0 of relay 138 and thereby close contacts a and b of that relay. Since the contacts of down limit switch 140 are open, coil 0 of.

time-delay relay 139 is deenergized and hold circuit 152 for coil c of relay 138 is completed through the normally closed contacts a of relay 139 and through the closed contacts b of relay 138. The closing of contacts a of relay 138 completes the energizing circuit 150 of' solenoid 119 so that valve 118 then supplies compressed air from header 101 through conduit 120 to space 87 of cylinder 75, and through branch conduit 137 to latch assembly 126. The compressed air supplied to latch assembly 126 disengages latch bolt 128 from the keeper recess in ram 14 thereby to permit displacement of the ram for moving shoe 11 from its rest position. The supplying of compressed air to space 87 of cylinder 75 effects movement of piston 79 to turn ram 14 in the direction moving shoe 11 outwardly toward basket side wall 2. The speed of movement of the shoe outwardly to the basket side wall is adjustably controlled by the rate at which oil from cylinder space 122 can pass through restriction 124 into oil reservoir 125.

As the shoe swings outwardly toward the basket side' its rest position. As working tip 12 of the shoe nears the basket side wall, stop screw 114 acts against plunger 112 to displace the actuating arm 110 of valve 108 so that the latter then vents pilot chamber 98 of valve 94 to the atmosphere through restrictor 117. The fact that the air is exhausted from pilot chamber 98 through the restrictor or leak control valve 117 serves to delay the 10 shift of valve spool 96 by spring 97, whereby shoe 11 remains adjacent the top of the basket side wall for a time interval suitable for digging a complete swath of solids from the top of that wall.

When the pressure in pilot chamber 98 is reduced sufliciently, spring 97 shifts valve spool 96 to apply compressed air in cylinder space 51A and to vent or discharge air from cylinder space 51B. The compressed air applied in space 51A causes downward movement of ram 14 and shoe 11 so that the remainder of the wall of solids is dug away from the basket side wall by rotation of the latter against the lower edge and face of the downwardly moving shoe. The speed at which the shoe moves downwardly is controlled by the rate at which restrictor 107 of valve 94 permits the discharge of air from cylinder space 513. When ram 14 commences its downward movement, abutment 148 moves away from actuating member 147 of up limit switch 141 so that the contacts of the latter are opened.

When the shoe reaches the bottom of the basket side wall, abutment member 148 on the ram displaces actuating member 146 of down limit switch thereby closing the contacts of that switch and completing circuit 153 for energizing the coil c of time delay relay 139. The time delay relay 139 determines the interval of time during which shoe 11 remains at the bottom of basket 1 against side wall 2 thereof before being moved inwardly and upwardly for return to its rest position. If the solids are not being adequately cleaned from the basket, the length of that time interval may be increased by suitably adjusting time delay relay 139 for increasing the length of the time period between the initiation of energization of the coil 0 of relay 139 and the opening of the contacts a of that relay.

When time delay relay 139 times out, that is, opens its contacts a, hold circuit 152 of relay 138 is interrupted thereby deenergizing coil 6 of relay 138 and causing the openings of the contacts a and b of that relay. The opening of contacts a of relay 138 deenergizes solenoid 119 of valve 118, whereby air is exhausted from space 87 of cylinder 75 to permit springs 88 to turn ram 14 in the direction for moving shoe 11 inwardly away from basket side wall 2. During the initial inward swinging movement of shoe 11, stop screw 114 on arm 84 moves away from plunger 112 so that valve 108 returns to its normal position for applying compressed air in pilot chamber 98 of valve 94. Thus, valve 94 is returned to the position shown on FIG. 7 for again supplying compressed air to cylinder space 51B and discharging air from cylinder space 51A, whereby shoe 11 is moved upwardly. The speed of the upward movement of shoe 11 is controlled by the rate at which the exhaust of air from cylinder space 51A is permitted by the restrictor 106 of valve 94. The described sequence of operation of valves 118, 108 and 94, the fact that cylinder 51 has a far larger volume than cylinder 75, and the restrictor 106 all combine to ensure that the inward swinging of shoe 11 away from the basket. side wall will occur ahead of the vertical upward movement of the shoe.

Duringthe final inward swinging movement of shoe 11, arm 84 again actuates in limit switch 142 and, during, the final upward movement of the shoe, abutment 148 actuates up limit switch 141, so that the contacts of both switches 141 and 142 are simultaneously closed to energize signal 143 and thereby indicate the return of shoe 11 to its rest position. Since the deenergizing of solenoid 119 of valve 118 also causes the latter to vent air from latch assembly 126, latch bolt 128 of the latter is urged by spring 132 into engagement with keeper recess 129 of ram 14 when shoe 11 returns to its rest position at theconclusion of a discharge cycle, thereby to ensure that the shoe remains in its safe rest position until the initiation of the next discharge cycle.

'It will be noted that, with the described control systems for discharger mechanism 10, the completion of each movement of shoe 11 during the discharge cycle automatically gives rise to control conditions for eflecting the next movement of the shoe. Thus, the length of time for the movement of the shoe downwardly along the basket side wall is not predetermined, but rather may vary with the condition of the cake of solids lining the basket side wall i It will also be noted that the described discharger mechanism, while being power-operated and fully automatic in controlling the sequence of movements of the shoe during a discharge cycle, is arranged to achieve effective sealing of the curb so that the space within the latter may be under pressure or contain a corrosive atmosphere, and further that the discharger mechanism includes means, in the form of the latch assembly 126, by which inadvertent movement of the shoe from its safe rest position is positively prevented,

7 Although an illustrative embodiment of this invention has been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to that embodiment, and that var ious changes and modifications may be effected therein by those skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

What is claimed is:

1. A discharger mechanism for removing solids from a centrifugal basket rotatable within a fixed curb, said mechanism comprising a mounting means adapted to be fixed on the curb top over an opening in the latter, a vertical ram extending axially through the opening of the curb top and carrying a discharger shoe within the basket, said ram being movably supported by said mounting means to move said shoe outwardly to and axially along the basket side wall to discharge solids from the basket and then back to an elevated rest position spaced,

inwardly from the basket side wall, yieldable means urging said ram in one direction for moving said shoe inwardly away from the basket side wall, fluid pressure operated actuating means adapted to act on said ram in the direction opposed to, and with a force exceeding the force of said yieldable means so as to move said shoe outwardly to the basket sidewall, other fluid pressure operated actuating means for displacing said ram so as to move said shoe downwardly along the basket side wall for discharging solids from the basket and then upwardly for cooperating with said yieldable means in returning the shoe to said rest position, control means for supplying fluid under pressure to operate both said actuating means, and latch means normally engaging said ram to prevent movement of said shoe from said rest position and being releasable by fluid under pressure from said control means.

2. A discharger mechanism for removing solids from a centrifugal basket rotatable within a fixed curb, said mechanism comprising mounting means adapted to be fixed on the curb top over an opening in the latter, ,a vertically extending ram supported by said mounting means to move axially through the opening of the curb top and also to turn about the longitudinal axis of the ram, a discharger shoe secured to the lower end of said ram and adapted to be held by the ram within the basket, yieldable means urging said ram to turn in one direction for moving said shoe inwardly away from the basket side wall, fluid pressure operated actuating means for turning said ram in the opposite direction with a force exceeding the force of said yieldable means so as to move said shoe outwardly to the basket side wall, other fluid pressure operated actuating means for axially displacing said ram so as to move said shoe downwardly along the basket side wall for discharging solids from the basket and then upwardly to cooperate with said yieldable means in returning the shoe to an elevated rest position spaced inwardly from the basket side wall, control means for supplying fluid under pressure to operate both said actuating means, and latch means normally engaging said ram to prevent movement of said shoe from said rest position and being releasable by fluid under pressure from said control means.

3. A discharger mechanism for removing solids from a centrifugal basket rotatable within a fixed curb which defines a sealed space adapted to be pressurized, said mechanism comprising mounting means adapted to be fixed on the curb top around an opening in the latter, a vertically extending cylindrical ram supported by said mounting means to move axially through the opening of the curb top and also to turn about the longitudinal axis of the ram, annular sealing means slidably embracing said ram to prevent the escape of fluid under pressure through the curb top opening from the sealed space within the curb, a discharger shoe secured to the lower end of said ram and adapted to be held by the ram within the basket, yieldable means urging said ram to turn in one direction for moving said shoe inwardly away from the basket side wall, fluid pressure operated actuating means for turning said ram in the opposite direction with a force exceeding the force of said yieldable means so as to move said shoe outwardly to the basket side wall, other fluid pressure operated actuating means for axially displacing said ram so as to move said shoe downwardly along the basket side wall for discharging solids from the basket and then upwardly to cooperate with said yieldable means in returning the shoe to an elevated rest position spaced inwardly from the basket side wall, control means for supplying fluid under pressure to operate both said actuating means, and latch means normally engaging said ram to prevent movement of said shoe from said rest position and being releasable by fluid under pressure supplied by said control means for operating said actuating means.

4. A discharger mechanism for removing solids from a centrifugal basket rotatable within a fixed curb which defines a sealed space adapted to be pressurized, said mechanism comprising a housing adapted to be fixed on the curb top around an opening in the latter, a vertically extending cylindrical ram slidably. supported by said housing to move axially through the opening of the curb top and also to turn about the longitudinal axis of the ram, annular sealing means slidably embracing said ram to prevent the escape of fluid under pressure through the curb top opening from the sealed space Within the curb, a discharger shoe secured to the lower end of said ram and adapted to be held by the ram within the basket, yieldable means in driving relation to said ram and continuously urging the ram to turn in one direction for moving said shoe inwardly away from the basket side wall, power operated actuating means carried by said housing for turning said ram in the direction opposed to, and with a force exceeding the force of said yieldable means so as to move said shoe outwardly to the basket side wall, other power operated actuating means contained within said ram for axially displacing the ram so as to move said shoe downwardly along the basket side wall for, discharging solids from the basket and then upwardly to cooperate with said yieldable means in returningthe shoe to an elevated rest position spaced inwardly from the basket side wall, control means for supplying power. to operate both said actuating means in a predetermined sequence, latch means carried by said housing and normally engaging said ram to prevent movement of said shoe from said rest position, and power operated means releasing said latch means to permit movement of the shoe from its rest position upon supplying of power from said control means for operating both said actuating means.

5. A discharger mechanism for removing solids from a centrifugal basket rotatable within a fixed curb, said mechanism comprising a base adapted to be fixed on the curb top around an opening in the latter, a cylindrical body extending vertically upward from said base and 13 being turnable relative to the latter about the longitudinal axis of said body, a cylindrical rarn within said body turnable with the latter and being longitudinally displaceable relative to the body to move axially through the opening of the curb top, a discharger shoe secured to the lower end of said ram and adapted to be held by the ram within the basket, yieldable means connected between said base and said body and urging said body and said ram to turn in one direction for moving said shoe inwardly away from the basket side wall, fluid pressure operated actuating means also connected between said base and body for turning said ram in the direction opposed to, and with a force exceeding the force of said yieldable means so as to move said shoe outwardly to the basket side wall, other fluid pressure operated actuati'ng means contained in said ram and connected with said body for axially displacing said ram so as to move said shoe downwardly along the basket side wall for discharging solids from the basket and then upwardly to cooperate with said yieldable means in returning the shoe to an elevated rest position spaced inwardly from the basket side wall, cont-r01 means for supplying fluid under pressure to operate both said actuating means, and latch means carried by said body and normally engaging said ram to prevent movement of said shoe from said restposition, said latch means having releasing means operated by fluid under pressure from said control means upon operation of both said actuating means to free said ram for movement of said shoe from said rest position. 6. A discharger mechanism as in claim 5; wherein said latch means includes a latch bolt mounted for radial movement through an opening in said cylindrical body and spring means acting. on said bolt to urge the bolt radially inward toward said ram, said ram having a keeper recess to receive said bolt under the urging of said spring means; and

wherein said releasing means includes a piston-like enlargement on said latch bolt and a cylindrical housing slidably receiving said enlargement of the latch bolt and having an inlet for fluid under pressure to act against said enlargement in the direction opposed to the force of said spring means on the latch bolt. 7. A discharger mechanism as in claim 5; further comprising annular sealing means carried by said base and slidably embracing said ram to prevent the escape of fluid under pressure through the curb top opening when the space within the curb is pressurized.

8. A discharger mechanism as in claim 5; wherein said other fluid pressure operated actuating means includes a cylinder within said ram and secured to the latter, a piston within said cylinder, and a piston rod extending axially upward from said piston out of said cylinder and being fixed to the upper end of said body, said rod having passages therein extending from said upper end of the body and opening into said cylinder below and above said piston so that fluid under pressure supplied through said passages is effective to cause said downward and upward movements, respectively, of the shoe.

9. A discharger mechanism as in claim 5; wherein said cylindrical body has at least one longitudinal slot and said ram has a lug extending radially outward therefrom and slidably engaging in said slot to cause said ram to turn with said body.

10. A discharger mechanism as in claim 5; wherein said control means includes a source of fluid under pressure, first valve means connected between said source and said latch releasing means and first mentioned actuating means and normally venting said first mentioned actuating means and said latch releasing means, first valve control means operative upon initiation of a discharge cycle to cause said first valve means to apply fluid under pressure in said latch releasing means and in said first mentioned actuating means so as to release the ram and effect outward movement of the shoe, second valve means connected between said source and said other actuating means, second valve control means normally positioning said second valve means so as to apply fluid under pressure from said source in said other actuating means in the direction for moving said shoe upwardly to said rest position, first abutment means turnable with said ram to act on said second valve control means when the shoe is moved outwardly to the basket side wall and thereby cause said second valve means to apply fluid in said other actuating means in the direction for moving said shoe downwardly along the basket side wall, and second abutment means movable longitudinally with said ram and acting on said first valve control means when said shoe reaches the bottom of the basket to cause said first valve means to return to its normal condition for venting said first mentioned actuating means so that said yieldable means cause inward movement of the shoe and said second valve control means responds to the corresponding movement of said first abutment means to cause said second valve means to again apply fluid under pressure in said other actuating means in the direction for effecting upward movement of the shoe to said rest position.

11. A discharger mechanism as in claim 10; wherein said first mentioned and other actuating means include respective cylinders in which the fluid under pressure acts to cause the corresponding movements of the shoe, and the cylinder of said first mentioned actuating means has a substantially smaller cross-sectional area than the cylinder of said other actuating means so as to effect the outward and inward movements of the shoe at a greater speed than the downward and upward movements thereof.

12. A discharger mechanism as in claim 10; wherein said first valve control means includes time delay means delaying the return of said first valve means to its normal condition when said second abutment means acts on the first valve control means, thereby to hold the shoe at the bottom of the basket side wall for a predetermined period.

13. A discharger mechanism as in claim 10; wherein said first valve control means includes an operating solenoid which, when energized, causes said first valve means to apply fluid under pressure in said latch releasing means and first mentioned actuating means, and an energizing circuit for said solenoid including limit switch means engaged by said second abutment means when the shoe reaches the bottom of the basket to interrupt said energizing circuit for the solenoid.

14. A discharger mechanism as in claim 10; wherein said second valve means has pilot means and is conditioned to apply fluid under pressure in said other actuating means in the directions for effecting said downward and upward movements of the shoe when said pilot means is vented and has fluid under pressure applied therein, respectively; and

wherein said second valve control means includes a control valve connected between said source and said pilot means to normally apply fluid under pressure therein, said control valve being actuated by said first abutment means when the shoe moves outwardly to the basket side wall to vent said pilot means.

15. A discharger mechanism as in claim 10; further comprising signal means to indicate the presence of the shoe at said rest position and including switch means engageable by said first and second abutment means, respectively, when said shoe is in its rest position and being connected in series to cause operation of the signal means only upon simultaneous engagement of both switch means by the respective abutment means.

16. In a discharger mechanism for removing solids from a rotating centrifugal basket by means of a discharger shoe which is moved outwardly to and downwardly along the basket side wall by the effect of fluid ing cylinder so as to return the shoe to a rest position; the

combination of latch means normally operative to hold the shoe in the rest position, release means operative by fluid under pressure applied therein to release said latch means and thereby permit the shoe to move from said rest position, a source of fluid under pressure, and sequenced control means selectively communicating said cylinders and said release means with said source so that said latch means can be released only when fluid under pressure is available at said source to be applied in said cylinders for efiecting controlled movement of the shoe.

17. In a discharger mechanism for removing solids from a rotating centrifugal basket by means of a discharger shoe which is moved outwardly to and downwardly along the basket side wall by the effect of fluid under pressure applied in first and second actuating cylinders, respectively, to discharge solids from the basket and then spring urged inwardly and moved upwardly by the effect of fluid under pressure applied in said second actuating cylinder so as to return the shoe to a rest position; the combination of latch means normally operative to hold the shoe in the rest position, release means operative by fluid under pressure applied therein to release said latch means and thereby permit the shoe to move from said rest position, a source of fluid under pressure, first valve means connected between said source and said release means and first cylinder and normally venting said reease means and first cylinder, first valve control means operative upon initiation of a discharge cycle to cause said first valve means to apply fluid under pressure in said release means and in said first cylinder so as to release said latch means and cause said outward movement of the shoe, second valve means connected between said source and said second cylinder, second valve control means normally positioning said second valve means so that fluid under pressure is applied in said second cylinder to move the shoe upwardly to its rest position, first abutment means movable horizontally with the shoe to act on said second valve control means when the shoe is moved outwardly to the basket side wall and thereby cause said second valve means to apply the fluid under pressure in said second cylinder in the direction for moving the shoe downwardly, and second abutment means movable ver tically with the shoe and acting on said first valve control means when the shoe reaches the bottom of the basket to cause said first valve means to return to its normal condition venting said release means and first cylinder, whereby the shoe is then spring urged inwardly and said second valve control means responds to the corresponding movement of said first abutment means to cause up ward movement of the shoe to the rest position.

18. In a discharger mechanism, the combination as in claim 17; wherein said first cylinder has a substantially smaller cross-sectional area than said second cylinder so that the outward and inward movements of the shoe occur at a greater speed than the downward and upward movements thereof.

19. In a discharger mechanism, the combination as in claim 17 wherein said first valve control means includes time delay means delaying the return of said first valve means to its normal condition when said second abutment means acts on the first valve control means, thereby to hold the shoe at the bottom of the basket side wall for a predetermined period.

References Cited UNITED STATES PATENTS 1,965,840 7/1934 Jones 210-376 X 2,063,472 12/1936 ThOll 210-375 2,703,035 5/1955 Hertrich 210 13s X 2,755,991 7/1956 Tholl et al. 210 375 X 3,038,611 6/1962 OConnor et a1. 210376 X FOREIGN PATENTS 204,937 10/1923 Great Britain.

OTHER REFERENCES Western States Machine Bulletin No. 3015, Roberts Centrifugals for the CPI, copyright 1961, 4 pages, 210 376. a

REUBEN FRIEDMAN, Primary Examiner.

J. DE CESARE, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,339,733 September 5, 1967 William Grieselhuber It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

'Column 2; line 7, for "tof" read of column 6, line 72, for "by displacement of plunger 112, then valve 108" read air from conduit 115 through conduit 116 to column 14, line 74, for "upwardy" read upwardly column 15, line 28, for "reease" read release Signed and sealed this 14th day of January 1969 (SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.

Attesting Officer 

1. A DISCHARGER MECHANISM FOR REMOVING SOLIDS FROM A CENTRIFUGAL BASKET ROTATABLE WITHIN A FIXED CURB, SAID MECHANISM COMPRISING A MOUNTING MEANS ADAPTED TO BE FIXED ON THE CURB TOP OVER AN OPENING IN THE LATTER, A VERTICAL RAM EXTENDING AXIALLY THROUGH THE OPENING OF THE CURB TOP AND CARRYING A DISCHARGER SHOE WITHIN THE BASKET, SAID RAM BEING MOVABLY SUPPORTED BY SAID MOUNTING MEANS TO MOVE SAID SHOE OUTWARDLY TO AND AXIALLY ALONG THE BASKET SIDE WALL TO DISCHARGE SOLIDS FROM THE BASKET AND THEN BACK TO AN ELEVATED REST POSITION SPACED INWARDLY FROM THE BASKET SIDE WALL, YIELDABLE MEANS URGING SAID RAM IN ONE DIRECTION FOR MOVING SAID SHOE INWARDLY AWAY FROM THE BASKET SIDE WALL, FLUID PRESSURE OPERATED ACTUATING MEANS ADAPTED TO ACT ON SAID RAM IN THE DIRECTION OPPOSED TO, AND WITH A FORCE EXCEEDING THE FORCE OF SAID YIELDABLE MEANS SO AS TO MOVE SAID SHOE OUTWARDLY TO THE BASKET SIDE WALL, OTHER FLUID PRESSURE OPERATED ACTUATING MEANS FOR DISPLACING SAID RAM SO AS TO MOVE SAID SHOE DOWNWARDLY ALONG THE BASKET SIDE WALL FOR DISCHARGING SOLIDS FROM THE BASKET AND THEN UPWARDLY FOR COOPERATING WITH SAID YIELDABLE MEANS IN RETURNING THE SHOE TO SAID REST POSITION, CONTROL MEANS FOR SUPPLYING FLUID UNDER PRESSURE TO OPERATE BOTH SAID ACTUATING 